High-speed steel

Speed ​​steel, best known for the the English name High Speed ​​Steel derived HSS ( abbreviation according to EN ISO 4957 HS) refers to a group alloyed tool steels up to 2.06% carbon content and up to 30 % proportion of alloying elements such as tungsten, molybdenum, vanadium, cobalt, nickel and titanium. These form the repeated annealing together with the carbon the relevant for the intended use secondary carbides.

In addition to high-speed steel, there are a number of other names for this type of steel. For example, the acronym HSS high speed steel or high (fast) are derived cut steel, but also high-speed steel is widely used. One or more hyphens are often added to the names to improve readability.

Properties

HS materials are characterized by high hardness, temper resistance, wear resistance and heat resistance up to 600 ° C. Titanium nitride coatings increase this hardness and wear resistance of the tool surface (especially cutting, chip breakers ) and significantly increase the way the corrosion resistance. They are mainly used in metal cutting machine tools, the cutting material for tools. Because of their properties, they allow higher cutting speeds than low-alloy tool steels, larger chip spaces and thus a higher metal removal rate per unit time. Compared with modern carbide or ceramic inserts the cutting speed for HS- tools are indeed much lower, but they are far less sensitive to shocks and vibrations, which result in the harder cutting materials sometimes very quickly to fractures ( eg, at the cutting edge). The lower fracture sensitivity allows further smaller wedge angle, which results in a lower surface roughness by itself.

Types of high-speed steels

  • HSS -R: shaping by rolling.
  • HSS -G: shaping by grinding ( G for ground ). Suitable for small tolerances.
  • HSS - E: shaping as HSS - G, but additionally alloyed with cobalt. This higher- and heat-resistant material is used for the processing of materials with higher strength and long cut channels with correspondingly strong heating.

The designation of HS steels is currently defined in the standard EN ISO 4957. It consists of the letters HS (after the detached previous standard DIN 17350: S) and following, separated by a hyphen, the average percentages of the alloying constituents of tungsten ( W), molybdenum ( Mo), vanadium (V ) and cobalt ( Co). Wish phrases see item # steel grade high speed steels.

After the alloying constituents of tungsten and molybdenum speed steels are generally divided into four groups with

  • 2% W, and about 1 % of Mo,
  • 12 % W and about 1% Mo,
  • 6% W, and about 5 % of Mo and
  • 18% W and about 9 % Mo.

Example: HS 12-1-4-5 contains about 12 % tungsten, 1% molybdenum, 4% vanadium and 5% cobalt.

Production

High-speed steels are austenitized after mechanical pre-treatment at about 1200 ° C to 1300 ° C in order to bring at these high temperatures, the stable carbide in solution. When quenching, there is an extensive transformation to martensite with residual, highly supersaturated with carbon austenite. After curing, these steels are annealed several times at about 550 ° C. Here are excreted by the only running slow, diffusion-controlled processes for a special carbides, involving the precipitation with it, and gradually reduced to the other at the same time, the carbon content in the austenite to this also as completely transforming to martensite.

Economic Importance

HS- cutting tools are usually used as a drill ( twist drill, center drill ), thread cutting tools, saw blades, milling and turning tools, but also as roller materials.

  • Tool material
  • Steel grade
Tempering (metallurgy) Tipped tool
395201
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